倾斜单桩复合地基受压变形特征与破坏模式试验研究

Experimental Research on Deformation and Failure Mode for Inclined Monopile Composite Foundation under Pressure

为了摸清桩体复合地基施工或服役过程中受侧向堆载或开挖产生的侧向作用而发生倾斜的受压变形规律变化情况,通过采用室内模型试验的手段,研究不同倾斜角度单桩复合地基受压变形规律及破坏模式,为倾斜桩复合地基质量评定提供依据。试验结果表明:(1)倾斜桩复合地基中,倾斜角在4°~10°范围内,相同荷载作用下,桩顶沉降随倾斜角增大而增大,上刺入量随倾斜角增大而减小。桩顶侧移有峰值,对应的倾斜角为“侧移临界倾斜角”。(2)桩身轴力随桩身倾斜角增大而减小,桩身摩阻力随倾斜角增大而增大。不同倾斜角单桩复合地基桩身受力产生弯矩,弯矩自上而下呈现“增大-减小”的变化规律,整体上呈“S”形,在桩身中上部出现峰值。(3)倾斜桩复合地基破坏模式存在地基沉降超限、桩身侧向失稳和桩身弯曲破坏。荷载增大时,倾斜桩沉降和侧移增大,地基沉降可能超限、桩身侧移增大、侧向失稳,荷载增加到一定值时,倾斜桩发生弯曲破坏,荷载继续增大时,地基沉降继续增大,超过容许值。处治倾斜桩时,建议加强桩身中上部抗弯刚度,采用轻质填料以减少荷载。

In order to understand the changes of compressive deformation law of pile composite foundation tilted by lateral load or excavation in the process of construction or service,the compressive deformation law and damage mode of monopile composite foundation with different tilting angles are studied by means of indoor model test,which provides the basis for quality assessment of inclined pile composite foundation.The results show that:①In inclined pile composite foundation,the settlement of the pile top increase and the deformation of the pile top spur into cushion decrease as the increase of the angle of inclination at the variation range of 4°~10°under the same load.There is an angle for the later movement of the pile top to get peak value.The angle is the“critical angle of later movement”.②As the increase of tilt angle,the axial force of the pile decreases and the frictional resistance of the pile increases.The inclined pile is subject to bending moment under load.The bending moment shows the rule of“increase-decrease”and the shape of“S”as a whole along the pile.There has a peak value on the middle-upper part of the pile.③The failure mode of the inclined pile composite foundation can be divided into over settlement of foundation,lateral buckling of pile,bending failure of the pile.As the load increase,the settlement and the lateral movement increase.The settlement may be larger than the limit.And the lateral movement of the pile increases which causes the pile gets later buckling.As the load increases to a determined value,the inclined pile gets bending failure.The load continues to increase,the settlement of the foundation also increases,and greater than the limit finally.Enhance the flexural rigidity of the middle-upper of the pile,and use light filling to reduce the load can be used to therapy the inclined pile.